21115255 has 16 divisors (see below), whose sum is σ = 29047104. Its totient is φ = 14434560.

The previous prime is 21115249. The next prime is 21115261. The reversal of 21115255 is 55251112.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21115249) and next prime (21115261).

It is not a de Polignac number, because 21115255 - 2¹⁹ = 20590967 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 14019 + ... + 15451.

It is an arithmetic number, because the mean of its divisors is an integer number (1815444).

Almost surely, 2^21115255 is an apocalyptic number.

21115255 is a deficient number, since it is larger than the sum of its proper divisors (7931849).

21115255 is a wasteful number, since it uses less digits than its factorization.

21115255 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1866.

The product of its digits is 500, while the sum is 22.

The square root of 21115255 is about 4595.1338391825. The cubic root of 21115255 is about 276.3962269188.

Adding to 21115255 its reverse (55251112), we get a palindrome (76366367).

The spelling of 21115255 in words is "twenty-one million, one hundred fifteen thousand, two hundred fifty-five".